Horizontal distribution of tintinnids in the open waters of the South Adriatic (Eastern Mediterranean)

Abstract

The horizontal distribution of oceanic tintinnids was studied in the South Adriatic Sea during 11 cruises undertaken between 1980 and 1990. Of the 70 species identified, there were 47 surface, 16 subsurface, 4 mid-water, and 3 deepsea species. The dominant surface and subsurface species were Dictyocysta mitra and Codonella aspera. Undella claparedei. Parundella lohmanni predominated in the mid-water layers and Xystonellopsis scyphium in the deep-sea layers. Ingression of water masses from the Ionian Sea and the formation of a cyclonic gyre are important in determining the horizontal distribution of tintinnids in the South Adriatic. Periods of strong advection of waters from the Ionian Sea impose a longitudinal type of distribution on tintinnids, characterized by high species diversity, low abundance, and the transport of southern species to the Middle and North Adriatic. This differs from "eddy type" distribution, in which species diversity is lower, population density is greater in all layers, and the transport of species northward ceases. It may be assumed that mesopelagic and deep-sea tintinnids depend on food resources transported by sinking Middle Adriatic dense waters (MadDW).